During World War 2 Finnish Army used three types of armored fighting vehicles, which it listed as assault guns. From these three vehicle types the most controversial, least well known and undoubtedly most unsuccessful was BT-42, only 18 of which Finnish industry built by installing British World War 1 era 4.5-inch howitzer installed with a new larger turret on top of tank chassis taken from captured Soviet BT-7 tank. The second assault gun to serve with Finnish Army was not only the most numerous German-manufactured armored fighting vehicle of 2^nd World War, but also the only modern armored vehicle used by Finnish Army in any real numbers during battles of summer 1944 and proved remarkably successful in hands of Finnish crews – Sturmgeschütz 40 G(STU 40 G). The last and also least of the three assault guns as far as importance in Finnish use is concerned, was JSU 152. Only two of these heavy Soviet assault guns were taken to Finnish use and from those two the only one sent to battle was immediately lost.

MAP: Map showing locaations of the most assault-gun related locations mentioned in this page. CLICK THUMBNAIL TO SEE LARGER PIC (170 KB).

PICTURE: The only surviving BT-42 assault gun - BT-42 Ps. 511-8, former R-708. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (141 KB).

While mobilizing for Continuation War that started in June of 1941, Finnish Army had concentrated its tanks to single existing Panssaripataljoona (Tank Battalion). The battalion gained excellent reputation leading Finnish offensive as spear-head from Tuullosjoki River to Syväri/Svir River and from there to city of Äänislinna / Petrozavodsk. Hence February of 1942 General Headquarters of Finnish Armed Forces decided to expand already this already famed battalion into Panssariprikaati (Tank Brigade), which was originally intended to contain three tank battalions, from which 3^rd Battalion was intended to be equipped with combination of captured T-28, T-34 and BT-series tanks. But since the total number of captured medium tanks proved to be too small for this purpose, the plan was changed in such way that ultimately Tank Brigade was to have two tank battalions and battalion named Panssaritykkipataljoona. Literally translated Panssaritykkipataljoona translates as Gun Tank Battalion or Armored Gun Battalion, which could be taken as a hint of the equipment it was to be equipped with – or just a very poor translation of Assault Gun Battalion. June of 1942 GHQ of Finnish Armed Forces issued orders for establishing this unit now known more aptly as Rynnäkkötykkipataljoona (Assault Gun Battalion), which along Tank Brigade was part of Armour Division (Panssaridivisioona). According orders the battalion was about to contain three assault gun companies, each of which was to be have six BT-series based vehicles equipped with British 4.5-inch howitzers. With notable exception of battalion commander and drivers, which were came from Tank Brigade, all officers, non-commissioned officers and men were transferred from variety of field artillery units with grand majority of them being volunteers.

STARTING POINT:

Officially Finnish Army knew this vehicle as 15 tonnin rynnäkkötykkipanssarivaunu BT-42 (15-ton assault gun tank BT-42). But in practice it was more commonly known as BT-42, BT-rynnäkkötykki (BT assault gun) and with nicknames "Christie", "Christian" and "Kristian" due to whole lineage of Soviet BT-tanks being originally based to Walter Christie’s tank design. Exactly how Finnish military came up with the decision to combine British 114 H/18 howitzer with captured BT-7 tank chassis is not known for sure, but using of captured BT-7 tank for the purpose was somewhat obvious choice. At that point there Armor Centre (Panssarikeskus), the main repair armored vehicle repair facility, still had large number of captured damaged BT-tanks for which Finnish military had no other use, while captured medium and heavy tanks had already been taken to Finnish use and even the number of repairable T-26 tanks not yet taken to Finnish use was rapidly dwindling. At least on paper BT-7 may have seem a good choice for the purpose since it had powerful 500 horsepower engine that could be expected to have no trouble working in much heavier vehicle and turret structure which allowed quite a large turret to be built on it. Also, since BT-7 model 1937 was the most recent manufacturing version of BT-series tanks, from all captured BT-series tanks it could be expected to provide the best starting point for conversion work. It is also possible that Soviet BT-7A artillery tank, even if not used by Finnish Army, may have served as inspiration of sort for the design.

PICTURE: Yard of Armor Centre, the main repair facility for armored vehicles photographed in June of 1942. Try to counting how my BT-series tanks are in it. Photographed by Military Official P. Jänis (SA-kuva.fi photo archive, photo number 102296). CLICK THUMBNAIL TO SEE LARGER PIC (156 KB).

The decision for choosing 114 H/18 light howitzer as the new main for this converted vehicle was much less obvious. Other options considered for this vehicle apparently included 76 RK/27 infantry gun plus light howitzers 122 H/09 and 122 H/10. As the Finnish abbreviation suggests this British Q.F. 4.5 inch Howitzer Mk 2, which for this purpose was now renamed as 114 Psv.H/18 (114-mm tank howitzer model 1918), had been introduced just year 1918, so by Finnish standards it was still relatively modern artillery design. If compared to other light howitzers used by Finnish field artillery 114 H/18 was among the lightest and short-ranged of its kind, but still closely comparable to Russian 122-mm World War 1 era light howitzers and their modernized versions commonly used by Finnish Army. It is true that if compared to most modern light howitzers of that time 114 H/18 had maximum range of several kilometers shorter, but this howitzer was also notably lighter than any of it more modern competitors. Ammunition used with 114 H/18 howitzer was separately loaded type (in other words – projectile and cartridge case containing bags of propellant were loaded separately). While this reduced practical rate of fire and was an obvious handicap, separate loading was de facto standard for all light howitzers in Finnish inventory at that time – including even the most modern of them. During Winter War Great Britain had donated 24 of these howitzers and another 30 howitzers had been bought from Spain, so there were plenty of them available. It is not known who selected this particular howitzer for the purpose and why it was chosen over other altenatives, but there are reasons to suspect that field artillery might have had strong motives to make this particular howitzer available for the purpose due to less than altruistic reasons. As far as field artillery was concerned 114 H/18 was caliber-wise non-standard howitzer with some less than spectacular features, rather poor reputation and uncertain future ammunition supply.

DEVELOPMENT OF BT-42:

Valtion Tykkitehdas (State Artillery Factory) had originally been established not long before World War 2 mainly for the purpose of locally manufacturing antitank-guns, anti-aircraft guns and field artillery pieces, production licenses for which Finland had acquired from Bofors. This factory had started its production only in year 1938 and had since become mainly major repair facility for artillery weapons. Now it received the difficult task of both designing this intended armored fighting vehicle and building it – even if the factory had no experience of even repairing armored vehicles – much less building one. Hence the starting point for the whole development was far from ideal. At that time Finnish industry as a whole had no previous experience about developing or manufacturing of armored motor vehicles beyond single Sisu armored car built for police use in year 1937. In addition the materials provided for the purpose limited possibilities of the design work in nothing less than extreme manner. Typically designing of armored fighting vehicle will require making choices for finding balance in between size of main gun, thickness of protective armor and size & power of engine - with each choice affecting other(s). But in this case the existing available materials being BT-7 tank chassis with its engine and 114 H/18 howitzer left very little room for making any sort of choices in these matters - and as it later became evident resulted handicaps of both tank and howitzer used being inherited to the resulting vehicle. Not only did State Artillery Factory not have any experience about armored vehicles, but probably due to the factory originally being intended to manufacture already existing artillery weapon designs, it had very little personnel capable for developing technical designs. Yet, ultimately the unenviable assignment for developing the resulting vehicle fell onto factory design of modest size of just dozen persons lead by engineer Oiva Rehnström.

Noting that designing assault gun based on BT-7 tank chassis was challenging would be an understatement. Not only was BT-7 tank chassis quite narrow, but it had driver’s station set in middle of the front hull – hence installing any kind of gun in the front hull would have been very difficult and required considerable changes. This is what likely explains why the design team decided to rather equip the vehicle with a new turret large enough to house specified 114 H/18 howitzer and two crew members. Some might argue that due to its rotating turret BT-42 was not really technically an assault gun, even if followed the basic concept of modifying vehicle to take larger gun than what the chassis had been originally intended for.

While 114 H/18 howitzer had been equipped with "pepper-box" muzzle brake and had rather modest muzzle velocity, its recoil still caused problems on BT-7 chassis. The turret ring and lower part of BT-42 turret both originated from Soviet BT-7 with rest of BT-42 turret being welded on top of Soviet-made lower turret section. While resulting BT-42 turret was both large and high, there were good reasons for that. Even with its muzzle brake and recoil length adjustment apparatus 114 Psv.H/18 howitzer still needed almost whole length of the turret for its parts moving backwards in recoil if fired at zero elevation. The new turret also had to be high enough to allow the howitzer achieve reasonably high elevation necessary for indirect fire, which with recoil forces also caused some additional problems. Mechanical claw mechanism was added to the design to allow temporarily locking the turret to chassis to make sure that the turret would stay on its place when the howitzer was fired. This new turret was only lightly armored, but its armor protection was on similar level as rest of the vehicle – in such level it only provided protection against shell fragments and small arms fire. As it was BT-42 was already heavier than what its suspension had been designed for and adding thicker armor even only for the turret would have only made it even heavier – which would have undoubtedly caused additional problems.

The optical equipment used with BT-42 turret also left much to desire. This new turret was equipped with single periscope and two prisms – combined with the howitzers dial sight these gave the vehicles crew even poorer visibility outside the vehicle than original optical instruments used in BT-7 tanks. The optical gun sight used for 114 Psv.H/18 tank howitzer was old Russian dial sight recycled from 76 K/02 light field gun and while useable, far from ideal for this purpose. The actual howitzer was manually aimed by gunner, who was using hand wheels. The horizontal gun laying system originated from BT-7, while the vertical gun laying system was a modified design based to one originally used in 114 H/18. Using both hand wheels simultaneously was impossible, which resulted gun laying system being quite slow to use. Elevation range of the howitzer was -5/+25 degrees.

500 horsepower M-17T gasoline engine coming to the design with BT-7 tank was liquid-cooled and based to aircraft-engine. It was also one of the most successful parts of BT-42 design, admitted this engine had been earlier criticized by Finnish military due to its high fuel consumption. While 72-octane aircraft gasoline used by Finnish military with this engine was obviously notably more flammable than diesel already used in most Soviet tanks at that time when BT-42 was introduced, M-17T engine had not just merely enough power for additional weight of BT-42, but it even made the vehicle quite fast on road. However the suspension and narrow poorly designed tank tracks, which had spoiled off-road mobility of BT-7 tank, also ruined the off-road mobility of BT-42. While diesel engine would have been a better alternative, they were not available and since Finnish industry at that time was incapable of even manufacturing truck engines – much less designing new tank engines and manufacturing them. As poor as the suspension and tracks were, when needed they allowed the tank to be driven on road wheels with chain drive, even if this feature was not really useful and could only be used on good roads. As the Finnish drivers would learn, the vehicle was heavy to steer, but fast on a good straight road - too bad such roads were a rare on Finnish – Soviet front. When it came to off-road mobility BT-42 could successfully operate off-road only in easy terrain and even then only if the ground was not too soft. The vehicle had fuel tanks for 650 liters of gasoline (*) with its engine spending during driving on average 100 liters / hour. If compared to other armored vehicles the maintenance interval of BT-42 was also exceptionally short with the vehicle requiring major overhaul after every 150 hours of use.

What is known the first BT-42 was apparently delivered to Assault Gun Battalion at that time stationed in city of Äänislinna / Petrozavodsk in 5^th of September 1942, with the early testing presumably concentrating on driving and mobility, since apparently these assault guns did not get change to test shooting live ammunition with their howitzers until April of 1943. Already the first tests revealed that BT-42 was exceptionally poorly suited for antitank-use - or in general poorly suited for combat use against other armored vehicles. The distribution of work was such that State Artillery Factory took care of actual conversion work from BT-7 to BT-42. In other words State Artillery Factory built all BT-42 turrets, installed them on each vehicle and equipped each turret with howitzer and optical instruments. Once this conversion work had been done each BT-42 was sent to Armor Centre (Panssarikeskus), which installed rest of the equipment and did other finishing touches before sending the completed vehicles to Armor Division.

Other companies directly involved in converting BT-42 were engineering works Oy Lokomo Ab and Crichton-Vulcan shipyard. Lokomo inspected and repaired six of the BT-7 tank hulls before they were used for the conversion and also shaped the steel plates needed for making BT-42 turret. Armor Centre inspected and repaired other twelve BT-7 tank hulls used for the purpose. Crichton-Vulcan tempered the steel plates once Lokomo had shaped them. All but one BT-42 was built on BT-7 model 1937 tank chassis, that one exception was Ps. 511-19, for which BT-7 model 1935 chassis was used. During the conversion process the chassis went through only few relatively small modifications. The most notable of these was adding screens to air intake and building new frontal parts for mudguards. Each vehicle had a three man crew – commander/gunner in right side of turret, loader in left side of turret and driver in middle of front hull. The vehicle had no secondary armament installed to it in addition of the howitzer. But each BT-42 carried inside the turret Suomi m/31 submachine gun and few 70-round drum magazines, which the crew could use if necessary. When it comes to radio and interphone equipment, there exists a serious contradiction between vehicle manual, equipment inventory lists and information recorded from those who once served in these vehicles. According official manuals BT-42 was supposed to be equipped with captured 71-TK-1 radios and TPU-2 interphone systems – both of them inherited from BT-7 tanks. However Finnish troops had noted 71-TK-1 so unreliable, that it was not commonly used. Nor is there any 71-TK-1 radio present in inventory equipment lists of Separate Tank Company in year 1944. Hence while 71-TK-1 could have been used early on, it apparently did not see large-scale use with BT-42. According equipment inventory lists year 1944 Separate Tank Company had P-12-7 radio transmitter-receivers for all its BT-42 assault guns and photographs taken inside the only remaining vehicle show that it still has equipment presumably intended for this radio. Former crew members however do not seem to remember these vehicles having been equipped with radios, so either P-12-7 was not really issued either, or for some reason rarely used.

PICTURE: BT-42 assault gun rear view. Notice hatch on top of the turret, turret rear door, vision slits and round pistol ports. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (116 KB).

IMPROVEMENTS:

As noted the first BT-42 was delivered to Assault Gun Battalion in early September of 1942, later that month after being found unsatisfactory it was returned to State Artillery Factory with list of necessary improvements, which included:

• Turret rear armor was just 10-mm thick, it had be increased to 16-mm.
• Turret had only one prism and it was not sheltered enough. The factory added 2^nd prism and built protective covers for them.
• Horizontal gun laying system was heavy to use (probably due to increased weight of turret), the solution was to provide 2^nd hand wheel for loader to allow both gunner and loader to rotate turret when needed.
• Hole of the gun sight in top of turret was gathering branches and other debris while driving under trees. Folding protective cover was added for it.
• The howitzer recoil mechanism cover was only 4-mm thick making it vulnerable even to small arms fire. Its armor protection was increased to 5 – 10 mm level.
• Ammunition storage location and arrangement were unsatisfactory. In addition ammunition storage interfered with battery maintenance. Ammunition storage was re-designed and battery was moved into armored battery box placed on mudguard.

The intended timetable for deliveries of BT-42 failed already early on – with actual production getting running about 3.5 months late from planned schedule. This was probably much due to limited capacity of involved parties and prioritization. Armor Centre had been ordered to handle repairs of medium and heavy tanks as priority one, repairs of light tanks as priority two and work related to BT-42 assault guns with only as priority three. Still, the production succeeded catching up with the first 13 vehicles being delivered less than four weeks behind schedule. But delivery of the five last vehicles suffered considerable delay – they were delivered over 18 months behind the schedule in late autumn of 1943. This delay was at least partly due to improvements, which needed to be implemented to both already delivered vehicles and the ones that were still to be converted. Hence all already converted assault guns returned back to State Artillery Factory for improvements and were off from active service. Production-improved BT-42 assault guns were delivered for one company of Assault Gun Battalion at the time in delivery batches of few vehicles. 1^st Company received its first BT-42 assault guns in 26^th of February 1943, 2^nd Company received its first assault guns in 23^rd of March 1943 and 3^rd Company got its first assault guns in 14^th of May 1943. Eleven BT-42 manufactured early on received their individual identification with R-number system, but with introduction of new Ps. identification number system, while last seven production vehicles received Ps. number starting with Ps. 511.

Even after the improvements based to list above had been implemented BT-42 was found to be far from satisfactory. The basic design of the vehicle had such problem points, that they caused serious concern. Major V. Luovila (commander of Assault Gun Battalion at that time) reported about BT-42 to commander of Tank Brigade in 4^th of May 1943 that: "Due to the experience gathered, especially because of the vehicles poor off-road mobility and slow rate of fire, I do not consider this vehicle to be suitable as an assault gun."

The production-improved BT-42 was still found have plenty of issues with its structural design and equipment. So 20^th of May 1943 Assault Gun Battalion introduced second list of improvements, which now included:

• The hatch on top of the turret was to be made larger. State Artillery Factory refused to do this due to structural integrity of the turret roof, which had been welded from several armor plates.
• Ammunition storage was unsatisfactory, State Artillery Factory answered by suggesting improved storage solution.
• The field of view for the gun sight was limited by protective armor, which State Artillery Factory succeeded improving by increasing size of the hole made to front turret for this gun sight.
• Travel lock system was required for the howitzer also when the turret was pointing to vehicle’s six o’clock. This was added.
• The vertical (elevation) gun laying system hand wheel ratio needed to be slower, in other words the gunners apparently found need for its hand wheel to be lighter and allow more precise aiming. State Artillery Factory refused to change the ratio, but suggested replacing hand wheel with larger version.
• Howitzer recoil system had issues with its gaskets. Solution was developed for these problems.
• Howitzer gun sight attachment had too much production tolerance, which needed to be eliminated.
• The battalion also requested better quality of work for rest of the vehicles.

PICTURE: BT-42 assault gun rear view. Notice metal boxes on mudguard. Adding such boxes on both mudguards was one of Finnish modications - these boxes housed not only toools needed for the vehicle but also its batteries.(Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (159 KB).

FIELD TEST AND CONCLUSIONS WITH FAR-REACHING CONSEQUENCES:

In June – July 1943 1st Company of Assault Gun Battalion was sent to frontline in River Syväri / Svir to field-test BT-42 assault gun and its howitzer. The assault guns used by 1^st Company for this were R-704, R-708, R-710, R-713 and R-717. This field-test was such that BT-42 assault guns were used to destroy targets such as machinegun nests and bunkers located on other side of the river – mostly with direct fire, but also indirect fire was occasionally used. While this field-testing was apparently quite limited, with the assault guns firing from prepared positions and did not fit to much more versatile role reserved by German military for assault guns, as a whole the operation was a success. With 1,279 howitzer shells fired BT-42 assault guns succeeded destroying about hundred targets and damaging equal number. One soldier was killed by return fire and another wounded. All assault guns involved survived this first battle of theirs, with only R-710 being damaged by enemy fire and even its damages were slight. Also technical issues proved to be surprisingly small – just one engine failure and some issues with suspension and locking system.

While this field-test was a success, it apparently failed to raise much of hope concerning suitability of BT-42 for its intended purpose. Before the field-tests had even ended, chief of staff for Armor Division reported about BT-42 in 10^th of July 1943: "…experiences gathered by this far indicate that the vehicle is much less suited to be used as an assault gun than expected" and suggested modifying BT-42 as armored personnel carriers. General Headquarters of Finnish Armed Forces apparently did not take these expert estimations seriously and turned them down noting that BT-42 had not yet been properly tested and noting the considerable financial expense already spent for building BT-42 assault guns. The true low point was that since Armor Division had clearly indicated that it had no faith for success of BT-42 assault gun, Armed Forces GHQ responded by suggesting transferring these vehicles elsewhere and creating of another unit not serving as part of Armor Division, even if this was the unit where tracked armored vehicles had otherwise been concentrated. However all this negative feedback may have produced also something positive. In May of 1943 Armed Forces GHQ decided to order 45 Sturmgeschütz 40 G assault guns from Germany. While Germany accepted to deliver only 30 of these latest assault guns to Finland in year 1943, Assault Gun Battalion obviously did not have enough personnel to operate both these new German assault guns and existing BT-42 assault guns. In addition Armor Division HQ noted that due to its unsuitability for assault gun role BT-42 could not be used along new Stu 40 G in the same unit.

Hence Armor Division HQ suggested two options, both of which required creating a new military unit for the specific purpose:

• Separate Self-propelled Artillery Battery (Erillinen Panssaripatteri) (with 6 x BT-42): This unit would have been used mainly for indirect fire and would have served as self-propelled field artillery unit for Armor Division.
• Separate Tank Company (Erillinen Panssarikomppania) (with 12 x BT-42): This unit would have been used mostly for direct-fire regardless of its limitations.

From these two options Self-propelled Artillery Battery would have likely been more useful. One of the strange things concerning Armor Division was that with-in its own organization it actually had much less mortars and field artillery than a normal infantry division. What it lacked compared to normal infantry division was field artillery regiment and regimental-level mortar companies with 120-mm mortars. Hence additional artillery battery equipped with 114-mm self-propelled howitzers would have been most welcome addition to its resources. Also, while BT-42 made exceptionally poor assault gun or tank, it could have been somewhat successful self-propelled howitzer. But from these two options Armed Forces GHQ chose Separate Tank Company option, even if Armor Division suspected that due to poor capability of BT-42 for this sort of use as a tank, the unit would be unlikely to see much actual use. While even the commanding officers of Armor Division apparently had been having problems grasping the difference in between tank, assault gun and self-propelled howitzer, Armed Forces GHQ was apparently completely clueless in the matter and suitability of BT-42 for these roles.

November of 1943 Armed Forces GHQ established Separate Tank Company (Erillinen Panssarikomppania), which was to be equipped with twelve BT-42 assault guns. Assault Gun Battalion started handing over its BT-42 assault guns in 30^th of October 1943 and 7^th of December 1943 BT-42 assault guns were officially transferred to Separate Tank Company. This new unit commanded by Lieutenant Stig Sippel got its soldiers with transfers from Tank Brigade, Assault Gun Battalion and other units of Armor Division. Regardless its official intended role this unit rained its BT-42 crews to use of both direct fire and indirect fire.

Early on Separate Tank Company had its 14 BT-42 organized as HQ-unit equipped with two BT-42 assault guns and two platoons each having six BT-42. But by 10^th of June 1944 organization of the company was changed in such manner, that it had just 11 assault guns organized in following manner:

• HQ-unit (2 x BT-42)
• 1^st Platoon (3 x BT-42)
• 2^nd Platoon (3 x BT-42)
• 3^rd Platoon (3 x BT-42)

PICTURE: Column of tanks photographed in demonstration of tanks arranged in town of Enso just days before starting of Soviet offensive in Carelian Isthmus. Very few wartime photographs of BT-42 exist, but this is one. The armoured vehicles shown in the photograph are from left to right T-26 R-124, T-50 R-110, Landsverk Anti II R-902, BT-42, T-34 Ps.231-2 and T-28 (probably R-102 or R-103). Photographer Military official Hedenström. (SA-kuva photo archive, photo number 151591). CLICK THUMBNAIL TO SEE LARGER PIC (114 KB).

VIIPURI BATTLE 20^th OF JUNE 1944:

Soviet offensive that started in Carelian Isthmus 9^th of June 1944 ended the long trench-war period in Finnish – Soviet front. The battles fought in that summer also proved the flaws of BT-42 with 8 out of 14 vehicles operated by Separate Tank Company being lost that summer with battle of Viipuri (Wiborg / Wyborg) in 20^th of June 1944 becoming the swan song of this unit. Separate Tank Company had already lost three BT-42 assault guns in 17^th - 18^th of June during its previous operations without any serious battle. Five additional BT-42 assault guns were lost in this single battle and the aftermath following it. By the time the Soviet offensive in Karelian Isthmus reached city of Viipuri it had already breached Finnish frontline defenses and VT-line, forcing Finnish troops in western part of the front to retreat. Finnish Army had hastily brought in 20^th (Infantry) Brigade to defend the city in defensive positions earlier built in its eastern suburbs and Separate Tank Company was subjugated to this brigade for that task. 20^th Brigade was inexperienced infantry brigade, which containing four infantry battalions and two field artillery battalions. The brigade was commanded by Colonel Armas Kemppi, who was capable officer, but like grand majority of Finnish officers he had very little experience about using armored vehicles. So it does not come as a surprise that apparently he did not grasp the difference in between tanks, assault guns or self-propelled howitzers – much less the differences in their tactical use. Hence once Lieutenant Sippel reported to his brigade headquarters and suggested that the nine remaining operational BT-42 assault guns of Separate Tank Company would take positions inside the city in Linnasaari Island and support the brigade with indirect fire, but his suggestion was denied. Instead Colonel Kemppi decided to spread out its BT-42 assault guns along the frontline and use them for direct-fire to boost up the (admittedly) poor antitank capability of his troops. When it came to Viipuri battle of June 1944, this proved to be just one of the many errors of judgment from Finnish Armed Forces GHQ and Colonel Kemppi. The brigade had arrived to Viipuri with very little ammunition and failed to acquire ammunition supply until too late.

So all nine BT-42 were taken to frontline and driven to turret down type positions dug by their crews and infantry. Two of the companies platoons and command vehicles were supporting 2^nd and 3^rd Battalion of 20^th (Infantry) Brigade in eastern suburbs, while 3^rd Platoon supported 3^rd Battalion of 3^rd (Infantry) Brigade, which defended area north-east of the city. Since most of these assault guns were apparently missing working radios, spreading out the company in this manner also caused platoons having problem reaching company commander and other platoons.

MAP: Battle of Viipuri 20th of June 1944. CLICK THUMBNAIL TO SEE LARGER PIC (537 KB).

Composition of Separate Tank Company at that time

• HQ-unit (Lieutenant Sippel, 3 x BT-42): Positions in Ristimäki city sector, supporting 2^nd Battalion of 20^th Brigade.
• 1^st Platoon (2^nd Lieutenant Holmström, 2 x BT-42): Positions in Karjala city sector supporting 3^rd Battalion of 20^th Brigade.
• 2^nd Platoon (2^nd Lieutenant Kaakinen, 2 x BT-42): Positions in Maaskola railyard of 2^nd Battalion of 20^th Brigade.
• 3^rd Platoon (2^nd Lieutenant Saarinen, 2 x BT-42): Positions in Tammisuo north-east of city supporting 3^rd Battalion of 3^rd Brigade.

The Soviets first showed up early in the morning with infantry supported by tanks appearing in front of 2^nd Battalion of 20^th (Infantry) Brigade in Ristimäki. BT-42 assault guns of 2^nd Platoon opened fire against T-34 tanks with their howitzers using HEAT-shells, but without any visible results. By 09:30 large concentrations of Soviet infantry and some 50 – 70 tanks had been spotted. Liuetenant Sippel’s command vehicle BT-42 R-717 took part in shooting indirect fire to these targets, but was damaged by return fire and had be pulled back for repairs towards Ristimäki. Finnish infantry continued repulsing Soviet attacks until around noon. Headquarters of 2^nd Battalion/20^th Brigade had been repeatedly attacked by Soviet aircraft, so at that time Major Bäckman commanding the battalion decided to move back his battalion HQ about 500 meters, which may have partially caused the later events. Also another BT-42 assault gun was now in need of repairs, hence around 12:15 they were towed back with other two BT-42 – four assault guns had left the frontline in Ristimäki and Maaskola, but not without infantry noticing it and possibly making false conclusions. The panic that started with false rumor of order for retreat started to spread among 6^th Rifle Company of 20^th (Infantry) Brigade around 12:30 and soon spread to adjacent 5^th Rifle Company, who both retreated in panic. This started a wide-spread chaos in sector defended by 2^nd Battalion. Around 13:30 Major Bäckman ordered his whole battalion to retreat, but failed to report this to brigade Headquarters. 20^th (Infantry) Brigade’s other battalions launched counter-attacks to recapture the trenches in Ristimäki from which 2^nd Battalion had retreated, but without success. Around 14:00 Lieutenant Sippel had taken his BT-42 and reported to Headquarters of 20^th (Infantry) Brigade asking permission to pull back his assault guns to Linnasaari Island in western side of the centre of Viipuri and provide fire support from there, but Colonel Kemppi refused this claiming that the assault guns were trying to escape and ordered them to fight inside the city.

While troops of 20^th Brigade were retreating through the city, 3^rd Platoon of Separate Tank Company was busy fighting in Tammisuo, where it was supporting 3^rd Battalion of 3^rd (Infantry) Brigade. At afternoon Soviet SU-122 assault gun and four T-34 tanks drove into firing sector of 2^nd Lieutenant Saarela’s BT-42 R-702, which fired 15 HEAT-shells at them from distance of just 70 meters – but none of the shells made any made any real impact. Now that the enemy had spotted this assault gun, it had to retreat and while doing so got stuck. The second BT-42 of this platoon R-713 suffered problem with its electric wiring, being was taken back for repair and evacuated.

Back in the city both BT-42 assault guns of 1^st Platoon had been converted to run on wheels with chain-drive, in Karjala city district 2^nd Lieutenant Holmström’s BT-42 511-7 fought a very desperate and one-sided battle against KV-series (or IS-series) heavy tank – hitting it 18 times with HEAT-shells without any real impact. While fighting against Soviet antitank-gun Holmström’s BT-42 got stuck in a ditch and had be abandoned. When Lieutenant Sippel did not return from brigade HQ Separate Tank Company’s 2^nd in command Lieutenant Nieminen took remaining three BT-42 assault guns that had earlier been pulled back for repairs and took them to Linnasaari Island. On its way back from brigade HQ Sippel’s BT-42 R-717 run into Soviet troops near city hospital and fired six HE-shells at them, before being attacked by T-34, which hit it to turret in crossroads of Eliaankatu and Kannaksenkatu streets, immediately killing both Lieutenant Sippel and loader Private Sorvisto. Only driver succeeded getting out of the destroyed command assault gun and reaching Finnish lines. Once Finnish infantry had retreated from the city to north-west, 2^nd Lieutenant Kaakinen’s BT-42 R-709 destroyed part of road bridge across Kivisillansalmi sound to make sure that the Soviets would not be able to use it to further continue their advance. What remained of Separate Tank Company was pulled away from frontline and transferred to Hanhijoki. HEAT-ammunition used with howitzers of BT-42 had proved totally useless during Viipuri battle, proving the vehicle defenseless against enemy tanks. At the same time the mobility issues had proved so serious even in city conditions that most of the assault guns had been abandoned as a result. It is worth noting that with exception of R-717 losses were not directly caused by enemy fire, but technical issues and poor mobility combined with rapid retreat causing creating situations in which the vehicles were immobilized and could not be salvaged in time. Even with losses of so many vehicles, their crews had been fortunate to survive Viipuri battle without heavy loss of men.

PICTURE: Sideview of BT-42 Ps.511-8 assault gun. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (130 KB).

Separate Tank Company manpower strength:

• 1^st of May 1944: 5 officers + 17 NCO + 65 men.
• 5^th of July 1944: 4 officers + 17 NCO + 58 men.

5th of July 1944 commander of Tank Brigade issued orders about disestablishing of Separate Tank Company. That same day Headquarters of Finnish Armed Forces (Päämaja) officially declared numerous armored vehicle models obsolete - included to these was also BT-42 assault gun. All remaining ten BT-42 assault guns were gathered placed in storage at Military Technical Depot (Sotatekninen Varikko). These remaining ten vehicles remained in storage for several years, during which time they received no repairs. Even if being declared obsolete already year 1944, the final decision about scrapping the nine last remaining BT-42 assault guns was not made until year 1951. Luckily one of them was saved for museum use and is now in Parola Tank Museum. That sole survivor is BT-42 Ps. 511-8, former R-708, which was transferred to museum collection in year 1961.

PICTURE: Stu 40 G assault gun Ps. 531-18. Notice the correct Finnish World War 2 era three color camo painted on this assault gun and shield for DT deck machine gun . (Photo taken in Parola during 95-year parade of Armored Troops). CLICK THUMBNAIL TO SEE LARGER PIC (120 KB).

When it comes to unit-type German assault gun units were descendants was in elite field artillery formations which had worked in close co-operation with infantry, providing it direct-fire fire-support. In 1930’s German Army had realized that manhandled field guns were no longer the best tools for this and decided to introduce armored vehicle for the purpose – assault gun. The resulting vehicle was Sturmgeschütz (assault gun), first of which (StuG Ausf. A) was introduced to use of German Army in February of 1939. This first version set the basic design of the vehicle. It was built on chassis of Panzerkampfwagen III and was equipped with low-velocity 75-mm StuK 37 gun installed to hull of the vehicle. Unlike tanks this vehicle had no rotating turret. Tactics-wise its intended use also differed from the role that the German Army had reserved for tanks. Originally assault gun was intended as infantry support weapon that would be used against enemy infantry. But ultimately assault guns also found themselves being used as antitank-weapons. Originally 75-mm StuK 37 gun with short L/24 was used as main armament of this assault gun, but since this gun was not powerful enough to reliably effective against tanks like T-34 and KV-1, it was replaced with longer and more powerful guns. The versions equipped with these longer guns were:

• Stu 40 Ausf. F: 75-mm StuK 40 L/43 gun.
• Stu 40 Ausf. F/8: 75-mm StuK 40 L/48 gun.
• Stu 40 Aust. G: 75-mm Stuk 40 L/48 gun.

While the longer more powerful gun was the most significant change made for StuG 40 assault gun during its manufacturing, it was just one of many. When manufacturing version shifted from Ausf. F to Ausf. G in December of 1942, armor protection in front hull and in front of driver was significantly increased. Other important features first introduced with Ausf. G was commander’s cupola, which had not been earlier used in assault guns. This version also lacked the box-like structures in upper sides of combat compartment used in earlier versions. Ausf. G became the de facto standard assault gun model for German military in 1943 and remaining in mass production until end of the war in 1945, it also became not only the most produced version of Stu 40 assault gun, but the most numerous German armored fighting vehicle of World War 2. In total about 9,000 vehicles of all production versions (Ausf. A – Ausf. E) of Sturmgeschütz 40 were manufactured, with about 8,400 vehicles representing versions Ausf. F or Ausf. G. Main manufacturers of Stu 40 G assault gun were Alkett (Altmärkische Kettenwerk GmbH), who manufactured this assault gun model from December of 1942 to April of 1945 and MIAG (Mühlenbau und Industrie Aktiegesellschaft) which started manufacturing it in February of 1943. Originally German Army (Heer) and Waffen-SS issued assault guns to separate assault gun battalions and brigades, which were then made subordinate of some Army Corps or Army. However towards end of the war German assault guns saw ever increasing use as tank destroyers. Due to shortage of materials starting year 1944 the Germans were also using them as replacement of tanks in tank divisions and tank destroyers in infantry divisions.

STUG 40 AUSF G:

As mentioned StuG 40 G assault gun was built on chassis of PzKw III medium tank. Like most assault guns it had no turret and had main gun attached to hull front superstructure. Hence in combat situation the whole vehicle had to be turned towards the enemy instead of just rotating the turret – requiring even more closely tuned co-operation in-between crew members than a normal tank with rotating turret. The StuG 40 G radius of turn was just 5.85-meters and gun had mounting allowed traverse of 20 degrees, but obviously maneuvering the whole vehicle instead of rotating turret was slower. This assault gun had relatively good mobility on road, but had its limitations as far as off-road mobility was concerned. It had torsion bar suspension and 300 horsepower Maybach HL 120 TR 12-cylinder V-12 gasoline engine. Transmission had six forward gears and reverse gear. Shortly noted both weight of the vehicle was quite high for engine of that size and along high ground pressure. From these two issues the high ground pressure apparently proved so serious, that the Germans decided to try fixing it. Even if this assault gun already originally had wider (40 cm) tracks than PzKw III or PzKw IV medium tanks, the Germans introduced for it ostketten ("east-tracks") to provide it yet wider tracks. Early ostketten were add-on extension parts for track shoes, but later on become complete tracks with wider track shoes. The operational range of this assault gun was also rather limited, it had fuel tank of 310 liters, but also average (on-road) fuel consumption of about 2 liters/kilometer.

PICTURE: Rear view of Stu 40 G assault gun Ps. 531-6 "Liisa". During summer of 1944 this assault gun knocked out nine Soviet tanks. Notice correct World War 2 Finnish three color camo painted on this vehicle. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (141 KB).

In typical German manner each StuG 40 G assault gun was equipped with Fu 15 and Fu 16 type 10-watt radio (transmitter & receiver) and interphone. Command-version of the vehicle had two radio sets – 10-watt and 30-watt, from which 10-watt radio was a platoon and company-level radio with limited range (*) while 30-watt Fu 8 radio had notably longer range (**) and was therefore suitable for communicating in-between units. By standards of that time this assault gun version had relatively good armor protection. Since there were several manufacturers and this assault gun was manufactured both as new vehicles and by recycling used PzKw III hulls, there were several production variations of how armor protection had been constructed. For example 80-mm thick front hull armor could be combination of 50-mm steel plate on the bottom and 30-mm steel plate bolted or welded on top of it – or with late production vehicles simply single 80-mm steel plate. There were also two versions of gun mantlet – early version that was angular and later cast more rounded version, which the Germans also referred as "saukopfblende"(boar head cover). All vehicles had been covered with anti-magnetic zimmerit paste, which had little practical use.

As often with armored vehicles, there was a variety of official and less official names & abbreviations for this assault gun version. Early on when assault gun was introduced to German use their military simply called it sturmgeschütz (assault gun), since there were no other designs to mix up with. But especially once PzKw IV medium tank based Sturmgeschütz IV was introduced, there was obvious need to separate the two - hence PzKw III tank based assault guns got named as Sturmgeschütz III or Sturmgeschütz 40. Hence, also Ausf. G (version G) was named accordingly. The longest of officially used names used from it seems to have been Gepanzerte Selbsfahrlafette für Sturmgeschütz 7,5-cm Sturmkanone 40, Ausführung G (Armored self-propelled vehicle for 7.5-centimeter assault gun, version G). But Sturmgeschütz 40 G was also referred as Sturmgeschütz IIIG or simply as StuG 40 G or StuG III G. Competing design based to PzKw IV chassis, Sturmgeschütz IV was manufactured in 1943 – 1945. In addition there was Sturmhaubitse 42 (StuH 42), which was basically Sturmgeschütz 40 G assault gun chassis equipped with 105-mm howitzer instead of 75-mm gun.

Total production according German Waffennamt:in:

• StuG III: 8,416
• StuH 42: 1,299
• StuG IV: 1,141

In addition of serving with German military until end of the war, these assault guns were also sold by Germany to friendly or neutral countries. German deliveries of assault guns during World War 2:

• Rumania: 120
• Finland: 59
• Bulgaria: 55
• Hungary: 40
• Spain: 10
• Italy: 5
• unknown country: 2

PICTURE: Stu 40 G assault guns in parade in Enso at 4^th of June 1944. Persons in VIP-stand of this parade included Marshal Mannerheim and President Ryti. Closest assault gun in Ps. 531-27 belonging to Lieutenant Myllymaa, commander of 1^st Platoon of 3^rd Company. Eleven days later this assault gun was hit by Soviet antitank-gun in Battle of Kuuterselkä. The hit killed Lieutent Myllymaa, but driver Lance Corporal Tuusa succeeded driving the vehicle into safety while under heavy fire. Later the assault gun was repaired and returned to service. Photographed by Military Official Hedenström (SA-kuva.fi photo archive, photo number 151593). CLICK THUMBNAIL TO SEE LARGER PIC (84 KB).

FINNISH ACQUISITIONS:

General Headquarters of Finnish Armed Forces (Päämaja) made the decision about acquiring of assault guns from Germany in spring of 1943. Reply of German OKW (Oberkommando der Wehrmacht) to the Finnish request concerning selling these vehicles was positive, so 45 assault guns Sturmgeschütz 40 G were included to acquisition treaty 1189, which was the last of three large acquisition treaties (1187 – 1189) containing military equipment that Finland acquire from Germany in 1941 – 1944. The price that Germany asked for Stu 40 G assault guns it exported was higher than what German military paid for the similar assault guns and varied from export country to another. When it came to Finland the price was 1.5 times the price paid by German military – 165,000 Reichsmark for normal Stu 40 G and 168,000 Reichsmark for the command version with Fu 8 radio, being equivalent of about 5.5 million Finnish Marks in Finnish currency of that time.

However probably due to political issues between the two countries ultimately only 30 of the 45 assault guns listed in the acquisition treaty were ever delivered to Finland. These 30 assault guns were shipped to Finland in summer – autumn of 1943 three deliveries:

• S/S Aldebaran, 6th of July 1943: 10
• S/S Argo, 10th of August.1943: 8
• S/S Leo, 3rd of September 1943: 12

All these assault guns were brand new plus equipped with standard German equipment kit and (dunkelgelb) paint job of that time. When they arrived assault guns were taken to Armor Centre (Panssarikeskus), where they were inspected, repainted with Finnish standard issue three color camouflage, nationality markings and Ps-numbers. At the same time small metal plates with markings of each vehicle’s individual Ps-number were added to both sides of the hull. Also original German MG-34 machinegun on top of the vehicle was replaced with DT-machinegun installed to folding shield on top of the vehicle. For this purpose the hole through this folding shield was expanded. In addition were also numerous other smaller modifications made at that time.

Assault Gun Battalion (Rynnäkkötykkipataljoona) received its first Stu 40 G assault guns in 2^nd of September 1943. Most wartime modifications were implemented in Assault Gun Battalion after the particular Stu 40 G assault guns had been issued there in 1943. These modifications made by June of 1944 included:

• Removal of skirt armor (schürtzen) with its attachment points – presumably because they were considered impractical. Presumably done already in 1943.
• Wooden crate for tools and other equipment was added and installed on rear deck on top of the engine compartment.
• Spare road wheels placed on holders attached on sides of the hull to provide additional protection.

PICTURE: Stu 40 G Ps.531-5 near Tali in July of 1944. Soldiers on top of the assault gun are presumably its crew. This assault gun took part in Battles of Kuuterselkä and Tali-Ihantala before being lost in Battle of Vuosalmi against several T-34 tanks. Photographed by Military Official Unto Hämäläinen. (SA-kuva.fi photo archive, photo number 155642). CLICK THUMBNAIL TO SEE LARGER PIC (135 KB).

Soviet offensive that started in Karelian Isthmus in 9^th of June 1944 changed situation with Germany since it rejuvenated German interest for providing Finnish military additional weaponry desperately needed for stopping the Soviets. German Oberkommando der Wehrmacht (OKW) issued orders to supply Finland with 10 PzKw IVJ medium tanks and 15 Stu 40 G assault guns per month. The total number of PzKw IVJ to be delivered was limited to 40 tanks, but deliveries of assault guns were to continue until further notice. These orders resulted total 29 Stu 40 G assault guns being delivered to Finland in June – August of 1944. This time the assault guns arrived with five ships:

• S/S Leo: 29^th of June 1944: 5
• S/S Anna, 2^nd of July 1944: 7
• S/S Argo, 6^th of July 1944: 3
• S/S Capella, 3^rd of August 1944: 6
• S/S Kollaa, 6^th of August 1944: 8

The official name that Finnish Army came up for Sturmgeschütz 40 G assault gun was 24 tonnin rynnäkkötykki-panssarivaunu Sturmgeschütz 40 (24-ton assault gun tank Sturmgeschütz 40 G), with the official abbreviation 24 Ryn.tyk.psv./Stu.40 – although Finnish crews soon nicknamed the vehicle simply as "Sturm" or "Sturmi". In typical manner Finnish Army selected Ps. registry number series for identifying individual vehicles, for these assault guns that number as Ps. 531 and numbers for individual vehicles being issued in systematic manner. Hence those Stug 40G assault guns that were acquired in year 1943 received individual numbers reaching from Ps. 531-1 to Ps. 531-30, while those acquired in 1944 got numbers from Ps. 531-31 to Ps. 531-59.

Finnish crews found out that Stu 40 G assault gun had better visibility outside their vehicle and better optical equipment than any other armored vehicle in use of Finnish Army at that time. Hence its crew was likely to spot enemy vehicle first and if the co-operation in between crew-members was smooth enough, also possibly able shoot first as well. And once the enemy tank was in sights the gun was effective enough to knock out any enemy armored vehicle from normal combat ranges and if necessary had good maximum rate of fire (up to 15 shots/minute) for follow-up shots. Also radios and interphone proved good allowing effective co-operation both in-between crew-members and assault guns. However "Sturmi" also had its own set of problem-points. As noted off-road mobility was not too great with engine somewhat weak for vehicle of this weight and the weight for each square inch of track was also quite high. Hence it was best to stay on roads and easy terrain. Road wheels also had problems surviving stress, which caused durability issues. In addition shedding a track or gear-box damage was not that rare occurrence either.

PICTURE: Stu 40 G Ps. 531-34 assault gun photographed in August of 1944. This vehicle has practically all of the Finnish modifications in it. Photographed by Lieutenant Colonel I. Frey (SA-kuva.fi photo archive, photo number 161481). CLICK THUMBNAIL TO SEE LARGER PIC (142 KB).

By summer of 1944 there were numerous other improvements introduced to most of those Stu 40 G assault guns, which were in active use of Assault Gun Battalion (*). Most of these improvements were intended to improve armor protection. Maybe the most visible of these was welded armor visor added for driver’s vision slit, which had four inch thick "bullet-proof" glass. Additional armor was added also to right side of front hull. As a finishing touch whole front hull on top of these was "rounded off" with ferroconcrete – presumably to get rid of any shot traps or other weak points. Also the sides of gun placement on both sides of gun mantlet received additional strips of armor and most vehicles got additional track links placed on front hull for additional protection. Armor was added also around commander’s cupola to improve its protection. While skirt armor (schürtzen) had already been removed earlier, now addition plate of armor was added to side hull in between road wheels. This 15-millimeter steel plate was installed in such way, that there was a 30-millimeter air gap in between it and side hull armor. Summer of 1944 many of the assault guns were equipped with three wooden logs installed on both sides of the vehicle on top of mud guards. Installing of these logs increased protection for upper part of side hull armor, but at the same time the logs were also practical tools for helping assault gun that had gotten stuck. Adding these logs resulted road wheels being removed and transferred to new location on rear hull. In addition of normal markings made already earlier, each driver (or tank commander if he did not come up with one) was allowed to paint name of his fiancé, wife etc to driver’s armor visor as further personalization of each assault gun.

(*) Only 24 out of 30 assault guns delivered in 1943 were in active use before June of 1944. The rest had been placed in storage, presumably for intention of replacing possible battle losses.

PICTURE: Well camouflaged Stu 40 G Ps. 531-42 assault gun in Battle of Vuosalmi. Machine gun's shield is missing - possibly removed for lower profile. As mentioned driver or tank commander often marked name of his fiancé, wife etc to driver’s armor visor. According conficting sources this vehicle might be bit of an exception to that rule - sources suggest that the name marked in driver's visor may have been Miller with photo of Hollywood actress with that name (possibly Ann Miller) glued on ferroconcrete above it. Photographed by 2^nd Lieutenant V. Hollming (SA-kuva.fi photo archive, photo number 156840) Nowadays this individual Stu 40 G is in collectons of Auto & Technik Museum Sinsheim in Germany. CLICK THUMBNAIL TO SEE LARGER PIC (144 KB).

1. Group in June – August of 1943: Three officers, 14 NCO and 22 men lead by Captain Werner von Troil (commander of 2^nd Company in Assault Gun Battalion). Other officers were Captain Kumlin and Engineer-lieutenant Lindberg. This group had five week course about operating assault guns in Sturmartillerieschule in Jütenbog. The course had some problems due to not having translators with it and because of that had to rely in (limited) German language skills of mainly its officers.
2. Group in November – December 1943: Four officers, 10 NCO and one man lead by Engineer-Major Guido Ruotzi (commander of Armor Centre repair facility). This course was mainly for technical personnel. The course was held in Sturmschützschule in Burg and Panzertruppenschule in Wünsdorf.

As a rule one should note that typically troops that do the fighting can only do as much as their support and supplies allow. Another matter due to which Assault Gun Battalion equipped with Stu 40 G assault guns in 1944 was notably different than any other unit of World War 2 era Finnish Army is, that this unit also got all the other specialist soft vehicles belonging to battalion of this type – five Büssing-NAG 4500 trucks with mobile repair shop, two Sd.Kfz half-tracks as salvage vehicles, radio vehicles, Kübelwagen command vehicles etc. Even Tank Brigade of Armor Division was not as well equipped when it came to specialist vehicles that helped to keep its tanks operational. It is worth noting that the reason for Assault Gun Battalion these soft vehicles being acquired for Assault Gun Battalion was not because Armed Forces General Headquarters or Armor Division Headquarters would have been smart enough to include them to original contact, but simply because officers sent to above mentioned courses noticed in Germany, exactly how important the specialist soft vehicles were for keeping the assault guns operational and on their own behalf decided to make sure that the acquisition included those vehicles. Soft vehicles acquired for Assault Gun Battalion were delivered to it in January – February of 1944.

SUMMER OF 1944:

Only those assault guns that had been delivered in 1943 saw real combat use in battles of summer 1944. If not before, due to its battle success, during that summer Assault Gun Battalion operating these assault guns gained itself a elite unit reputation. Finnish Stug 40 G assault guns were the only modern armored fighting vehicles used in any real numbers by Finnish Army at that time and they proved remarkably successful achieving higher tank vs. tank kill ratio than any other armored fighting vehicle model operated by Finnish Army. According official numbers summer of 1944 these assault guns knocked out total 87 Soviet tanks and assault guns while own combat losses were only 8 vehicles. The most successful Finnish crew was 2^nd Lieutenant Börje Brotell’s crew with gunner Corporal Olli Soimala, driver Corporal Sulo Kauppi and loader Private Armas Launikko - they knocked out 11 Soviet tanks and assault guns with their Stu 40 G Ps. 531-10 "Bubi". When it comes to Soviet armored fighting vehicles knocked out by Stu 40 G assault guns of Finnish Army both model of armoured vehicle and location are unknown for two knocked out vehicles. These assault guns did their work in three major battles:

• Kuuterselkä (14^th – 15^th of June 1944): 18 tanks and 3 assault guns.
• Tali-Ihantala (25^th – 29^th of June 1944): 39 tanks and 4 assault guns.
• Vuosalmi (11^th – 13^th of July 1944): 14 tanks and 6 assault guns.

Combat-related losses of Finnish Stu 40 G assault guns:

However combat-related losses were not the only thing that reduced the number of Stug 40 G remaining in operational use. Those who made the original contract about acquisition of assault guns failed to include it the stockpile of spare parts so vitally necessary for keeping them operational in wartime conditions. So the assault guns arrived along rather minimal number of spare parts and their further acquisitions were far too small to solve the problem. Hence the unfortunate Stug 40 G Ps. 531-13 got cannibalized for spare parts needed to other assault guns already in year 1943 and later Ps. 531-7, Ps. 531-28 and Ps. 531-53 all sent for repairs to Armor Centre shared its fate. All these four assault guns cannibalized for spare parts remained in official inventory lists until being removed from them in 24^th of October 1944.

In addition of 75-mm main gun, which Finnish military named Psv.K/40, these assault guns had typically captured Soviet 7.62-mm DT-machinegun installed with weapon shield on top of the vehicle in front of loader’s hatch. While some of the Stu 40 G assault guns had gun mantlet built for coaxial machinegun, base for remote-controlled machinegun and/or hole on the roof for Nahverteidigungswaffe smoke-mortar/close-defense weapon, the vehicles delivered to Finland had none of these weapons. While Finnish-used armored fighting vehicles typically had one Suomi m/31 submachine gun for the crew carried inside the vehicle, these assault guns had two such submachine guns.

After learning about Finnish – Soviet Armistice Treaty Germany immediately stopped all deliveries to Finland in 2^nd of September 1944. The deliveries stopped that day included ships in Danzig harbor already loaded with 7 Stu 40 G assault guns and 9 German-captured T-34 tanks, which now got unloaded instead being shipped to Finland. Ultimately Finnish Army ended up buying number of PzKw III tanks from Norway in year 1958 to get spare parts for remaining Stu 40 G assault guns. One of the special versions operated by German Army in its training facilities was driver training version of assault gun. Also Finnish Army found itself needing such vehicles. The solution to this problem was modifying two of the assault guns to such vehicles by removing main gun, installing new armor roof and closing the hole left behind by removed gun with a plate equipped with window. The first vehicle to undergo this modification was Ps. 531-21 which had been hit in Portinhoikka battle and never fully repaired, while the second one later modified in similar manner was Ps. 531-52. Summer of year 1956 these two driver training vehicles got their own series of Ps registry numbers becoming Ps. 631-1 and Ps. 631-2. The two vehicles were removed from driver training use and modified back to their original form as assault guns around 1958 – 1959. These assault guns remained in active use with Finnish Army until declared obsolete in year 1959. It is noteworthy that there were still 45 of them in Finnish army inventory of armored vehicles in end of that year – in other words they total number had not really dropped since end of World War 2. However even this removal of active use did not end their career with Finnish military, since starting year 1966 many of them were dug in as ad-hoc bunkers, which would have been used for defending most important air fields in case of war. One could argue how smart decision this actually was considering the quite limited traverse of their main gun.

PICTURE: Stu 40 G assault gun Ps. 531-45. This vehicle painted with post-war Finnish insignia and post-war modifications is the best of three Finnish Stu 40 G assault guns remaining in driving condition. The other two are Ps. 531-4 and Ps. 531-18. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (124 KB).

AMMUNITION:

Originally Stu 40 G assault guns ordered in year 1943 were supposed to be delivered with 1,200 main gun shots per assault gun with ammunition types being:

But by time the first ammunition deliveries had happened the numbers had changed to these:

Due to shortage of tungsten Germany dropped manufacturing of ammunition loaded with Pz.Gr 40 APCR-T projectiles. Hence this ammunition was included only to the first two deliveries and was no longer available after them. Finnish military got only 300 rounds with Pz.Gr 40 APCR-T projectiles. Deliveries of other ammunition types however kept coming with APHE-T being used to replace APCR-T.

However it is important to notice that the percentages of delivered ammunition do not directly reflect the distribution of ammunition that Finnish Stu 40 G assault guns carried to battle. Before battles of summer of 1944 typically about 75% of the ammunition carried in these assault guns was with HE-shells. But when it comes to actual battles of summer 1944, apparently the normal ammo distribution was 50% HE, while other 50% was mostly APHE-T, good number of HEAT-T rounds and probably few APCR-T rounds reserved for "hard customers".

PICTURE: ISU-152 assault gun "1212" - the sole survivor of the the two captured ISU-152 assault guns taken to Finnish use. As seen this vehicle was returned to its original form after its career as salvage vehicle had ended. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (141 KB).

The story of Soviet heavy assault guns started with SU-152 based on KV-1S heavy tank and designed & manufactured in Chelyabinsk, which at that time was the centre for manufacturing of heavy tanks in Soviet Union. By February of 1942 the Soviets had noted that their infantry needed heavy fire support capable of providing hard-hitting direct-fire on enemy strongpoints and that existing heavy howitzers lacked the needed mobility. Hence the pragmatic solution was to design self-propelled gun equipped with proven and capable 152-mm ML-20 howitzer. From three prototypes all based to KV-1S and introduced in December of 1942 Object 236 designed by Chelyabinsk Kirov Plant (ChKZ) proved highly successful and was officially approved to inventory of Red Army in February of 1943 and also placed to mass-production immediately after its approval. Early on it was referred as KV-14, but was renamed as SU-152 after only about two months after entering to production. Total production of SU-152 was about 700 vehicles. While the original intention behind heavy assault gun was to provide infantry support against fortified positions other strong points the design proved flexible enough to also serve as heavy tank destroyer. Due to capability of its 152-mm ML20S howitzer to knock out even the most heavily armored German vehicles when used in tank destroyer role, the Soviets nicknamed SU-152 assault gun "Zveroboy" ("Animal Killer"). On rare occasions this assault gun was apparently also used for indirect fire. SU-152 proved highly successful design with surviving vehicles serving Soviet Red Army until year 1954.

When new IS-series heavy tanks replaced earlier KV-series heavy tanks in production, also the heavy assault gun design needed to be upgraded to use new IS tank chassis. The design work started in July of 1943. The first prototype named IS-152 failed testing, but later improved prototype Object 241 completed in October of 1943 proved more successful. Object 241 passed tests, was officially approved in November of 1943 and it replaced SU-152 in mass-production by end of 1943. Concept-wise ISU-152 was obviously directly based to SU-152, but due to differences in chassis design had notably higher crew compartment.

This heavy assault gun had torsion bar suspension. It had crew of 4 or 5 men: Commander, gunner, driver and one or two loaders. Due to weight of howitzer shells and its ammunition being separately loaded, having two loaders would have probably been preferred situation, since even then the maximum rate of fire was only about 2 – 3 shots per minute. As typical to assault guns, there was no turret. The main gun was 152-mm howitzer, which had been installed to front hull slightly off centre and had limited traverse of 12 degrees to each side. The number of shells carried for this main gun was quite limited – just 20 shells, which was typically divided to 13 high-explosive (HE) shells and 7 armor piercing high explosive (APHE) shells. Only secondary armament installed to the vehicle was 12.7-mm DShK model 1938 anti-aircraft-machinegun installed on roof of the vehicle. Vehicle crew had rather poor visibility outside the vehicle and especially driver had very limited field of vision, which must have made driving the vehicle difficult. The howitzer had two sights – telescopic and panoramic. In addition roof hatches were equipped with periscopes. Each ISU-152 was also equipped with 10R or 10RK radio and TPU-4-BisF intercom system.

Sole manufacturer of ISU-152 was Chelyabinsk Kirov Plant (ChKZ). The total production of ISU-152 during World War 2 was 4,075 vehicles with another 2,450 being manufactured in post-war era by time the production ended in year 1955. Early on ISU-152 was based on IS-1 chassis, but later production versions were built by using chassis of IS-2 and IS-2 model 1944, which had both heavier armor protection, but also larger fuel tanks. Early version also had three hatches on its roof, while late version had four hatches on roof of the vehicle.

ISU-152 continued its career with Soviet Red Army also after ending of World War 2. At that time it went through two modernization programs – first in year 1956 as ISU-152K and second in year 1959 as ISU-152M. In these modernizations fuel tank was removed from combat compartment, which allowed increasing number of howitzer shells carried in vehicle to 30 shells. Another major improvement included to them was replacing of original engine with 580-horsepower 12-cylinder V-54 diesel engine of T-54 main battle tank and re-making of fuel tanks, these changes increased maximum range of the vehicle to 500 kilometers. Improvements made to howitzer and its ammunition also increased maximum range of main weapon considerably – up to 13 kilometers. Other improvements introduced better gun sights and adding of commander’s cupola. During 1959 modernization large number assault guns were modified as BTT-1 salvage vehicles, which in turn got modified as BTT-1T in 1960’s.

While Soviet Red Army was the main user of this assault gun and salvage vehicles based to it, the Soviets also delivered them to Poland, Czechoslovakia, China, Egypt, Yugoslavia and possibly Iraq.

PICTURE: This rather poor quality photo is one of the very few to show Finnish captured JSU 152 before its first and final battle. Only one of these assault guns was ever painted with Finnish wartime nationality insignia. While this vehicle is camoflaged with tree branches white hightlights of Finnish "hakaristi" nationality markings are visible next to the soldier in the front hull of the vehicle. Photographed by Military Official T. Norjavirta (SA-kuva photo archive, photo number 154795). CLICK THUMBNAIL TO SEE LARGER PIC (81 KB).

CAPTURED JSU 152 ASSAULT GUNS:

Finnish Army knew this assault gun as JSU 152 and captured two of them during World War 2. Both of these were captured 25^th of June 1944 near Portinhoikka crossroads during battles of Tali-Ihantala. One of the captured two vehicles was captured basically intact, even if abandoned by its crew. It was captured about 700 meters from Portinhoikka crossroads on road leading to Juustila. Taken immediately to Finnish use, it was quickly repainted with Finnish insignia and lost in battle just four days later near Kölni farm in near Portinhoikka in 29^th of June. That day it was sent to counter-attack with mixed four man crew gathered for the last minute – driver (Private Virtanen) had earlier served as driver of KV-1 and had some time to study the assault gun, but other three crewmembers were picked for the job just half-an-hour before launching the counter-attack and had earlier served in T-28 medium tank. JSU 152 was leading Finnish counter-attack from Portinhoikka crossroads on a city leading towards city of Viipuri when it found itself fighting two T-34/85 tanks. Captured JSU 152 fired at them, but missed its target. And then both Soviet T-34/85 tanks hit front hull of JSU 152, made its mixed crew to bail out and abandon the vehicle. Later Soviet-taken photographs indicate that this was probably a smart move, since the photos show signs of follow-up shots causing large explosion that destroyed the abandoned assault gun.

PICTURE: Captured JSU 152 "1212" had been loaded into train wagon. Previous battle damage, the two holes under gun mantle, is clearly visible in this photo. Photographed by Major H. Lappi (SA-kuva photo archive, photo number 152662). CLICK THUMBNAIL TO SEE LARGER PIC (81 KB).

The second captured JSU 152 assault gun was marked with Soviet tactical number 1212 and had earlier unrepaired battle damage – it had been shot through front hull under the gun mantle. This vehicle was found 230 meters from Portinhoikka crossroads on road leading to Juustila and had been immobilized by getting stuck on road bank. Also its right track was broken, which likely had caused the vehicle getting stuck on road bank. But this JSU 152 also still had crew well-armed and determined still inside the vehicle. 2^nd Lieutenants Schrey and Hiltunen with group of soldiers "smoked out" the crew of this immobilized vehicle and shot them in resulting firefight. This assault gun was sent for repairs to Armor Centre (Panssarikeskus) in town of Varkaus. However it never got a chance to serve Finnish Army as an assault gun. At that time Finnish Army was lacking armored specialist vehicle designed for salvaging medium and heavy tanks from battlefield. Hence Ps. 745-1 was modified as such specialist salvage vehicle called JSU 152V by removing its weapons and equipping the vehicle with towing equipment. Repairs and modification work for this sole JSU 152V salvage vehicle Ps. 745-1 was completed in November of 1944. Only weapon originally intended for Ps. 745-1 was 20-mm Lahti L-39 antitank-rifle installed on top of the vehicle as anti-aircraft weapon, but final vehicle had also ball mount for DT-machinegun in its front hull in place of howitzer. In addition this salvage vehicle had its engine equipped with powerful muffler to reduce changes of enemy spotting the vehicle too soon. This salvage vehicle that remained in use of Finnish Army until year 1964, at which point it was transferred to museum use and returned to original form with re-installation of its 152-mm howitzer, which had been in storage all those years. Nowadays the vehicle is in Parola Tank Museum.

REPORT:

One might wonder what Finnish Army thought about this assault gun. Apparently some testing had been done with the captured JSU 152 during four days before losing it. 14^th of August 1944 Major H. Mikkola (commander of 1^st Battalion/Tank Brigade) reported his opinion about JSU 152 to Major-General Ruben Lagus (commander of Armor Division). According the report Major Mikkola considered the vehicle to have the following advantages and disadvantages:

• Advantages:

1. Powerful artillery shell of the main gun.
2. Good shooting accuracy of main gun at least from short range (tested from shooting distance of 400 meters).
3. Powerful engine and improved side clutches.
4. Good armor protection.

• Disadvantages:

1. The vehicle is quite blind and completely helpless against short range anti-tank weapons (panzerfaust and panzerschreck).
2. Due to its weight the vehicle is clumsy.
3. Gun laying for the main gun is too slow.
4. Rate of fire for the main gun is too slow.

Shortly noted he came to conclusion that ISU-152 was poorly suited to combat against other armored vehicles, considered it to have poor off-road mobility, but thought it might be good for knocking out strongpoints of fortified positions.

PICTURE: Another view to JSU 152 "1212". This photo angle shows large mufflers and some attachment points used for towing equipment when this vehicle was JSU 152V salvage vehicle. (Photo taken in Panssarimuseo). CLICK THUMBNAIL TO SEE LARGER PIC (123 KB).

SOURCES:

Kapteeni P. Hovilainen: Tankkirykmentistä Panssaripataljoonaan 1919 – 1949.

Pekka Kantakoski: Suomalaiset Panssarivaunujoukot 1919 – 1969.

Pekka Kantakoski: Punaiset Panssarit, Puna-armeijan panssarijoukot 1918 – 1945.

Erkki Käkelä and Andreas Lärka: Suomalaisten rynnäkkötykkien kohtalot.

Esa Muikku ja Jukka Purhonen: Suomalaiset Panssarivaunut 1918 – 1997, The Finnish Armoured Vehicles 1918 - 1997.

Pekka Kantakoski: Panssarimuseo..

Panzerbuch der Tanks, Parts 1 – 3 by Fritz von Heigl

Heigl’s Panzerbuck der tanks, Parts 1 – 3 by O.H. Hacker, R.J. Icks, O. Merker and G.P.v. Zezchwitz.

Sturmgeschütze, Entwicklung und Fertigung der sPak by Walter J. Spielberger.

Sturmgeschütz 40 (L/43 & L48), the long gun versions by Horst Scheibert

Lecture of Jukka Purhonen: BT-42, suomalaisen rynnäkkötykin tekninen kehitys Panssariseminaari v. 2012.

Manual: 15 tonnin rynnäkkötykkipanssarivaunu, mallia BT42 (15 Ryn.tyk.psv./BT42) (printed 1944)..

Manual: 24 tonnin rynnäkkötykkipanssarivaunu, mallia STU.40 (24 Ryn.tyk.psv./STU.40) (printed 1945).

Article: Rynnäkkötykit Suomessa by Kari Kuusela in Suomen sotilas magazine 3/2004.

Article: Panssariässän arvio, "Sturmi" käyttäjiensä silmin by Pauli Thomelius in Suomen sotilas magazine vol. 3/2004.

Article: "Sturmi", Sturmschütz III Ausf. G, Suomen sotilas koeajaa, osa IX by Marko Eriksson in Suomen sotilas magazine vol. 3/2004.

Article: Panssarimiehen kesäkuu 1944 by Eero Parvio in Panssari magazine vol 1/2008.

Article: Panssaridivisioonan vastahyökkäys Juustilasta Talin edustalle, Osa 1 by Erkki Käkelä and Keijo Hiltunen in Panssari magazine vol. 1/2009.

Article: Panssaridivisioonan vastahyökkäys Juustilasta Talin edustalle, Osa 2 by Erkki Käkelä and Keijo Hiltunen in Panssari magazine vol. 2/2009.

Article: Panssaridivisioonan vastahyökkäys Juustilasta Talin edustalle, Osa 3 by Erkki Käkelä and Keijo Hiltunen in Panssari magazine vol. 3/2009.

Article: Ne 55 menetettyä part 1 and 2 by Erkki Käkelä in Panssari magazines volume 1/2014 and 2/2014.

Finnish national archives, archive folder T10925/6.

Finnish national archives, archive folder T10925/7.

Finnish national archives, archive folder T20206/F6.